1. Field of the Invention
The invention relates to steering systems.
2. Description of the Related Art
A steering system known in the related art transmits rotational motion of a motor to a ball screw mechanism through a toothed belt and pulleys so as to convert the rotational motion of the motor into linear motion of a rack shaft, thus assisting a driver in performing a steering operation. If the tension of the belt is reduced (or the belt is loosened), an increase in torque transmitted between the belt and the pulleys may cause the teeth of the belt to move out of engagement with the teeth of the pulleys, making it impossible to transmit the torque increased. To solve this problem, the steering system is provided with a belt tension adjusting mechanism to adjust the tension of the belt. The rack shaft, the ball screw mechanism, a speed reducer including the belt and pulleys, and the belt tension adjusting mechanism are housed in a rack housing of the steering system. The rack housing is made up of a combination of first and second rack housing members aligned axially.
A belt tension adjusting mechanism disclosed in Japanese Patent Application Publication No. 2007-112245 (JP 2007-112245A) includes: a base swingably supported on a rack housing via a pin; a tension pulley rotatably supported on the base and configured to come into contact with a belt; and a feed screw mechanism to press the base so that the tension pulley is pressed against the belt. Adjusting the feed of the feed screw mechanism controls the degree of pressing of the tension pulley against the belt.
Suppose that this belt tension adjusting mechanism is to be housed in the rack housing of the steering system known in the related art. In this case, the procedure for assembling the rack housing inevitably involves: assembling the motor, the speed reducer, and the belt tension adjusting mechanism to, for example, the first rack housing member in advance; adjusting the tension of the belt by the belt tension adjusting mechanism; and then assembling the first rack housing member and the second rack housing member to each other. This is because the tension of the belt cannot be adjusted after the belt tension adjusting mechanism is housed in the rack housing by assembling the first rack housing member and the second rack housing member to each other. Such a procedure makes it necessary to attach the motor to the first rack housing member, thus restricting the location of the motor. This means that the procedure for assembling the rack housing is fixed.